Autoimmune diseases, both for visceral organ or neuronal cells, are defined as “diseases where the destruction of one's own cells triggers the production of one's own antibodies against the destroyed cells or their ingredients and the destruction by one's own leucocytes is continued”. Further, as typical autoimmune diseases, for example, multiple sclerosis, myasthenia gravis, chronic rheumatoid arthritis, systemic lupus erythematosus, Sjögren syndrome, systemic scleroderma, insulin-dependent diabetes, idiopathic thrombocytopenic purpura, Hashimoto's thyroiditis, Basedow's disease (Graves' disease), pernicious anemia, Addison's disease, atrophic gastritis, hemolytic anemia, ulcerative colitis, etc. are known.
For treatment of autoimmune diseases, steroid hormones, immunosuppressants, etc. are widely used, but at the time of use, sufficient cautions are required over side-effects. Safety and highly effective drug has not yet been found. On the other hand, regarding the cause of autoimmune diseases, the involvement of T-cells has been pointed out. This is believed to arise when the helper T-cell type 1 (Th1)/helper T-cell type 2 (Th2) immune balance is lost. For example, it has been reported that before the relapse of one of the autoimmune diseases, multiple sclerosis, the production of the Th1 type cytokines IFN-γ, IL-12, etc. is observed and that the administration of IFN-γ increases the frequency of relapse of multiple sclerosis. That is, in conditions of multiple sclerosis and other autoimmune diseases, the shift of the Th1/Th2 immune balance toward Th1 bias may be considered to play a central role (P. Kidd, Altern. Med. Rev. 2003, 8, 223: Takashi Yamamura, Notoshinkei, 2001, 53, 707). On the other hand, as Th2 type cytokines shifting the Th1/Th2 immune balance toward Th2 bias, IL-4, IL-5, IL-10 are known, but their administration of itself causes the appearance of systemic side-effects, and clinical application of itself is therefore believed to be substantially impossible.
NKT cells are lymphocytes which express both NK cell markers (i.e., NKT receptors) and T-cell antigen receptors (TCR). T-cells recognize peptides bonded to major histocompatibility complexes (MHC), while NKT cells recognize glycolipids bonded to the CD1d molecules and produce a large amount of cytokines in an extremely short period of time, when stimulated from TCR.
For example, the (2S,3S,4R)-1-O-(α-D-galactosyl)-2-(N-hexacosanoylamino)-1,3,4-octadecanetriol (α-GalCer) having the formula (XIV):
is the first substance reported, as a ligand presented by the monomorphic CD1d expressed on dendritic cells and activating the NKT cells expressing T-cell receptors having semi-invariant α-chains (Vα14). It has been shown that it has a powerful antitumor activity and immunization action (see T. Kawano et al., Proc. Natl. Acad. Sci. USA. 1998, 95, 5690). Recently, the novel glycolipid OCH discovered by Yamamura et al. is a derivative in which the carbon chain of the sphingosine base part of α-GalCer is shortened and a ligand which similarly bonds to CD1d to stimulate the NKT cells, but α-GalCer causes NKT cells to produce IFN-γ and IL-4, while OCH more selectively promotes the production of IL-4 and shifts the Th1/Th2 immune balance toward Th2 bias (see K. Miyamoto et al., Nature 2001, 413, 531). Further, OCH effected in oral administration in a mouse experimental autoimmunological encephalomyelitis (EAE) model, and therefore, so is expected to be a new medicine in the area of autoimmune diseases. For the synthetic method of glycolipids as represented by α-GalCer, the Wittig reaction, as the key step, is in general used for constracting the carbon chain of the sphingosine base part (see M. Morita et al., J. Med. Chem. 1995, 38, 2176). However, the glycolipid having the formula (I) is a derivative, in which the carbon chain of the sphingosine base of α-GalCer is shortened, and therefore, so similar synthetic procedures like with α-GalCer proved to give low yields. Further, the glycolipid having the formula (I) was originally obtained by purification using ion exchange resin or HPLC, then converting into freeze dried materials. However, by the above method, large-scale facilities are required at the time of large-scale synthesis, and therefore, not only is there a problem of synthetic costs, there is also the major problem that the quality of the products may not be stable. Therefore, an efficient synthetic method for the large-scale production of the compounds having the formula (I) has not been known yet. Further, the synthesis of a glycolipid, where the substituent of the sphingosine base part is a substituted or unsubstituted cycloalkyl group, substituted or unsubstituted aryl group, or substituted or unsubstituted aralkyl group has not yet been reported.